Study on CO₂ adsorption properties of tetraethylenepentamine modified mesoporous silica gel

A novel tetraethylenepentamine (TEPA) modified mesoporous silica gel (SG) sorbent (TEPA-SG) for CO₂ capture was prepared by the wet impregnation method. The prepared samples were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analyzer (TGA), and N₂ adsorption-desorption technologies. Meanwhile, the effects of TEPA loadings and adsorption temperatures on the adsorption capacity were investigated in a self-assembled fixed bed reactor. Different weight percentages of polyethylene glycol (PEG) were added to TEPA-SG to study the promoting effect of hydroxyl groups on the adsorption capacity and regenerability. The results show that the SG modified by 40% TEPA has a maximum adsorption capacity of 2.21 mmol/g at 70 ℃ and atmospheric pressure. Moreover, the adsorption capacity increases to 2.70 mmol/g by adding a desirable amount of PEG, and after ten cyclic adsorption-desorption tests, the adsorption capacity is maintained at 2.66 mmol/g, demonstrating that as-prepared TEPA and PEG modified sorbent displays an excellent regenerability. In addition, the isosteric heat of adsorption based on the Clasius-Clapeyron equation approaches 30~40 kJ/mol, and decreases gradually with increasing the adsorption capacity, indicating that the surface of TEPA30/PEG10-SG sorbent shows an energetic heterogeneity.